Optical Frequency Domain Reflectometry (OFDR) has proven to be an effective system for measuring strain with high spatial resolution in optical fiber. See, e.g., U.S. Pat. Nos. 6,545,760; 6,566,648; 5,798,521; and 7,538,883. This high resolution capability has proven very useful in shape sensing applications. See, e.g., U.S. Pat. Nos. 7,772,541; 7,781,724; and U.S. Patent application 20110109898. Simpler strain sensing applications in single core fiber are described in U.S. Patent Application 20110247427.
OFDR achieves high spatial resolutions by acquiring data over a wide frequency range as a laser is tuned. In most applications, this tuning takes place over time as the laser is swept through a range of frequencies. It is assumed using this technique that the fiber under test is static, or unchanging, during the time of the sweep. If, however, the system being measured varies during the time that the laser is swept, the resulting measurement can be degraded. Such changes can be due to movement of the fiber under test or movement of the fiber optic leads that connect the fiber under test to the instrument. It would be desirable to achieve a higher quality measurement in the presence of such time varying changes.